Erythrocyte membrane ouabain-sensitive N a + , K + - ATPase of hypertensive Nigerians

Abstract

An assessment of the ATPase functions of erythrocyte membrane of newly identified subjects having essential hypertension shows that Na+, K+ -ATPase activity is higher in normal membranes than in membranes of individuals with essential hypertension. A study of the dependence of the enzyme on ATP in the presence of non-limiting concentrations of N a + (120mM) and Mg2+ (3 mM) shows that the pump in the membranes of hypertensive individuals, like that of normal humans, is easily saturable by ATP (≥2 µM). Analysis of the results of kinetic studies on the enzyme, in the presence of 5 mM K +, using the Hanes plot, reveals that, although the affinity (Km) of the pump for A TP is unaffected in essential hypertension, its maximum velocity (V max) is lower than in normal membranes. Even though the reason for a reduced sodium pump function in essential hypertension is not yet clear, it may not be unconnected with the presence of an endogenous inhibitor or with genetic or diet-induced membrane defects, as previously proposed by other workers in this area of research.